Featured Image auto-resizes and doubles if too small

If I put a small or long image as the feature image, it duplicates the image that shows up. I think I put in and then removed some code to auto-resize feature images, but I can’t find it. Example can be found here: http://www.justwritefood.com/archive/. I can’t seem to find what I’m doing wrong or how to fix it.

I want the featured image to show up just once, and be centered in the box. if it’s smaller than the box, i don’t care.